Pilots are commonly used for combustion applications for oil and gas processing, including burner management systems, flare stacks, process vessels, separators, boilers, line heaters and other burner applications for oil and gas processing. These pilots typically serve as an ignition source for a larger primary gas burner.
Pilot operation is critical because it impacts the efficiency, effectiveness, and safety of a burner application. Thus, monitoring the pilot flame to ensure flame presence and optimization may be crucial to effective operation of a combustion application for oil and gas processing. A flame supervision device may be used to monitor a pilot flame and control fuel flow and pilot ignition to prevent gas from flowing to the pilot if the flame is extinguished. A flame supervision device can be used to prevent dangerous unrestricted flow of gas without proper combustion. It may also be used for optimizing the pilot flame.
Flame rectification is a common method of flame detection used for burner applications at oil and gas well sites. In flame rectification, a flame sensor (flame rod or element) is configured so it may make contact with a pilot or burner flame. An alternating current is applied to the sensor so that when a flame is present the current flows from the sensor through the flame to a ground. When the surface area of one probe, such as a flame rod, is made smaller than that of the other probe, such as the ground, current tends to flow more in one direction, from the smaller surface to the larger one. Current can only flow when a flame is present, to conduct the ions through the ionized hot gas. Because the flame rod or sensor is smaller than the ground electrode, an alternating current (AC) applied to the flame sensor flows primarily in one direction and the AC current is rectified to a pulsating direct current (DC), or rectified current. This current can be used to signal a control module that a flame is present when a DC signal from the flame rod is present. Flame rectification relies on ionized gas formed during combustion, which may carry a small current.
Flame rectification systems for pilots commonly available in the industry typically include a flame sensor rod and a ground where the flame sensor rod is configured externally to a pilot nozzle and the ground may comprise the pilot nozzle or a separate ground electrode configured externally to the pilot nozzle. One of the challenges with flame rectification systems currently used in the industry is low accuracy or sensitivity when detecting flames in harsh environmental conditions or under low combustion conditions.
Also, pilot failures frequently occur in existing pilot systems due to improperly adjusted or loose externally mounted ignition and flame rods that are subjected to extremes in temperature and vibration. Wind and other environmental factors can shift the flame away from the flames' sensor rod or nozzle to prevent efficient flame detection and may also extinguish the flame. Also, within enclosed combustion applications, difficult environments inside of the firing enclosure can cause the pilot flame to be diverted away from the flame sensing rod causing premature shutdown, or may be extinguished altogether.
Some attempts have been made to address these issues. However, these attempts have been inadequate and pilot systems currently available in the industry may prematurely shut down when fuel pressure is low due to adverse environmental events such as icing or clogging and thus may be less reliable under adverse environmental conditions. Moreover, pilot systems attempting to overcome these issues are very expensive and the majority of pilots used in the industry continue to include externally configured flame sensor electrodes and ground electrodes.
It is thus desirable to have a pilot assembly, system, and method thereof for oil and gas processing that provides more robust flame detection and a more robust and durable flame under various operating conditions.